Sarcasm may be like a metal (5)
I believe the answer is:
irony
'sarcasm' is the definition.
(I know that sarcasm can be written as irony)
'like a metal' is the wordplay.
I cannot quite see how this works, but
'like' could be 'y' (similar in meaning) and 'y' is present in the answer.
'metal' could be 'ir' (Ir is an example) and 'ir' is found in the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'may be' is the link.
Can you help me to learn more?
(Other definitions for irony that I've seen before include "style of humour" , "Paradoxical sarcasm" , "situation showing incongruity" , "What "as clear as mud" demonstrates" , "type of discussion, originally" .)